The SD1 and SD1 32-voice are considered part of the VFX family, along with the VFX , VFX/SD, and VFX/SD II. They have compatible filesizes, and though their sound sets differ somewhat between models, a piano sound on one will be a piano sound on another, and so forth. The sequencer is RAM based, at least in the case of the SD1, so it can be updated to the latest version, 4.10 I think.
Someone correct me if I'm wrong but soundfiles traded outside this family won't work because the file size and details of the parameters will be wrong. Sequences MAY work in terms of notes but you'd have to set up something to convert the sound addresses to get the right instruments. Also are disk formats slightly different? Don't know! Your best bet would be to send sequences from one machine to the other by sysex and see if you can adjust the receiving machine to make the right sounds.If anyone can make this less confusing feel free.mn